Scottish Shortbread Mix in a Jar 1 1/2 cups all-purpose flour 3/4 cup powdered sugar 1/4 tsp. salt In a medium bowl, combine all the ingredients, blending well. Store in an airtight container. Attach to Jar: Scottish Shortbread Makes 16 pieces 1 cup butter, softened 1 package Scottish Shortbread Mix Preheat the oven to 300 degrees F. Knead the butter into the shortbread mix and press the mixture firmly into an 8-inch pie plate, or shortbread mold. Bake for 1 hour. The shortbread should be pale in color.